I've taken a list of English words, and examined each of them to see what they sound like (using the PHP metaphone function). This page lists the most common metaphone codes, along with their words. You can also search for a word of your own, and see which words sound similar - and which ones rhyme, and which ones alliterate.
loopy loop loppy lop lope loup lippy loupe lap lip leap lipa lipe
loopy goopy whoop dopey soppy roupy hoop hoppy coop copay copy goop loop loppy mopey mopy poop poppy ropey ropy soapy soupy dopy choppy
loo looey looie blooey blooie flooey flooie